I would recommend you add the idea of an indoor spin bike to your list of possibilities.
You can buy a new Lemond Revmaster bike for about $1000. You can enjoy all of the benefits of caloric burn, regulate your output and enjoy no impact to the joints. If you work your SOE in the 6-9 zones for an hour, you can burn 600-1000 calories in an hour.
http://www.lemondfitness.com/product...evmaster-sport